Apparatus, system and method for dendrite and roughness suppression in electrochemical structures

ABSTRACT

A method, and associated batteries and battery charging units, that involve inducing electric and/or magnetic fields (field-induced current) across an electrode of a electrochemical cell, such as an anode of a battery. The field and current across the electrode may be referred to herein as a transverse current as this current is typically transverse to the ionic charge current that may be applied when charging a battery. The field and current may be induced from connecting AC energy, e.g., AC current, across the electrode or at a discrete point or points of the electrode. The induced field and current may suppress dendrite growth, experienced in conventional batteries without AC energy, among other advantages.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims priority to U.S.Nonprovisional patent application Ser. No. 16/247,435 filed on Jan. 14,2019 entitled “APPARATUS, SYSTEM AND METHOD FOR DENDRITE AND ROUGHNESSSUPPRESSION IN ELECTROCHEMICAL STRUCTURES,” which claims priority under35 U.S.C. § 119(e) from U.S. Patent Application No. 62/617,103 filed onJan. 12, 2018 entitled “APPARATUS, SYSTEM AND METHOD FOR DENDRITE ANDROUGHNESS SUPPRESSION”, all of which are fully incorporated by referenceherein for all purposes.

U.S. application Ser. No. 16/247,435 is a continuation-in-part of U.S.Nonprovisional patent application Ser. No. 15/649,633 filed on Jul. 13,2017 entitled “ELECTROCHEMICAL METHODS, DEVICES AND COMPOSITIONS,” nowU.S. Pat. No. 10,697,083 granted Jun. 30, 2020, which claims priorityunder 35 U.S.C. § 119 to U.S. Provisional Patent Application No.62/361,650 filed on Jul. 13, 2016 entitled “ELECTROCHEMICAL METHODS,DEVICES AND COMPOSITIONS,” both of which are hereby incorporated byreference in their entirety for all purposes.

TECHNICAL FIELD

Aspects of the present disclosure involve electrochemistry, andparticularly electrochemical structures, such as a battery, and methodand devices for suppression of the growth of dendrites and the like inthe same.

BACKGROUND

Batteries generally comprise one or more electrochemical cells ofsources of a countercharge and first electrode layers separated by anionically conductive barrier, often a liquid or polymer membranesaturated with an electrolyte. These layers are made to be thin somultiple units can occupy the volume of a battery, increasing theavailable power of the battery with each stacked unit. As thesecomponents become thinner, they also become more fragile. Further, asthe electrodes become thinner, a larger ohmic drop occurs across thesurface leading to less uniform charge density during charge/dischargecycles. Further still, battery electrodes may obtain growths (ordendrites) during charge cycles of the battery that may further damagethe battery or degrade battery performance.

For example, lithium ion batteries typically have a metal oxideelectrode (M is typically iron, cobalt, manganese) and a carbonelectrode coated on metal current collectors. The metal oxide serves toattract and stabilize lithium ions during discharge of the battery andusually determines the cell's operating potential. The metal oxideelectrode is initially in an oxidized state while the carbon is graphiteinfused with lithium ions. During discharging (that is, normal use ofthe battery to provide power to a device), the Li⁺ ions diffuse betweengraphene layers to edge sites of the graphite, and then through thesolid electrolyte interphase (SEI). The SEI is a layer that forms whenlithium initially reacts with components of the organic electrolyte,comprised of inorganic and organic byproducts. Being less conductive toboth electrons and ions compared to the graphite and electrolyte,respectively, the properties and quality of the SEI tend to determinethe cell's overall performance. From the SEI, lithium ions continue todiffuse through the ion transport layer and toward the metal oxide,which becomes reduced to LiM_(x)O_(y). During charging, the Li⁺ ionsfollow the opposite path and instead ultimately diffuse back through theSEI and intercalate back into the carbon. Under ideal chargingconditions, lithium ions are able to enter the graphite at edge sites(rate limiting step) without excess polarization that might result inplating. Problems with plating arise if the cell voltage becomes toohigh, the electrode is too polarized, or the SEI is porous, non-uniform,or too thick or thin. In extreme cases, Li⁰ aggregation in the form ofdendrites may create an explosion hazard within the battery.Specifically, if the Li⁰ reaches the opposite electrode, the battery mayshort and the dendrites formed during the Li⁰ deposition may damage themembrane dividing the two divisions of the battery.

In the case of lithium metal electrodes or the event of plating ongraphite electrodes, the deposits become increasingly rough withsubsequent charge/discharge cycles. Lithium-metal batteries (Li-foilanode) and lithium-ion batteries (Li-ions intercalated into agraphite/foil anode, where the current collector is frequently copper)both suffer from the growth of lithium dendrites during the battery'scharging cycles. While Li-ion anodes can be stable for hundreds ofcycles, dendrites develop immediately in Li-metal. Once formed, thedendrites lower the coulumbic efficiency of the battery, damage the ionmembrane, and may short the battery if the dendrites contact the anode.Commonly dendrites form which puncture or irreversibly damage theelectrolyte membrane. If dendritic growth reaches the opposingelectrode, then the battery is permanently shorted and cannot berecovered.

It is with these issues in mind, among others, that aspects of thepresent disclosure were conceived.

SUMMARY

The following embodiments and aspects thereof are described andillustrated with systems, tools and methods meant to be exemplary andillustrative, not limiting in scope. In various embodiments, one or moreof the above-described problems have been reduced or eliminated, whileother embodiments are directed to other improvements.

Provided herein are methods for optimally maintaining the electrodes inan electrochemical cell, such as a battery, whether charging,discharging, or dormant. The methods suppress and reverse dendriticgrowth and control the quality and healing of the SEI, both commonsources of reduced performance and eventual failure for most batteries.

In particular, provided herein is a method comprising inducing electricand magnetic fields (field-induced current) across an electrode of aelectrochemical cell, such as an anode of a battery. The field andcurrent across the electrode may be referred to herein as a transversecurrent as this current is typically transverse to the ionic chargecurrent that may be applied when charging a battery. The field andcurrent may be induced from connecting AC energy, e.g., AC current,across the electrode or at a discrete point or points of the electrode.

A potential is induced across a surface of the electrode in the presenceof a chemical potential between an electrolyte and the surface of theelectrode. The induced potential propagates across and charges thesurface of the electrode. This electrode may be a first electrode in anymethod or device described herein.

Another embodiment involves a charging method comprising, in a batteryincluding a first electrode and a second electrode, applying a directcurrent (DC) charge current to one of the first electrode and the secondelectrode. In conjunction with applying the DC charge current, applyingalternating current (AC) energy to at least one of the first electrodeand the second electrode. The presence of AC energy may suppressdendrite growth, among other advantages discussed herein.

Aspects of the disclosure may further involve a battery chargercomprising a power supply including a first conductor and a secondconductor, where the power supply is configured to apply a directcurrent (DC) charge current through the first conductor to one of afirst electrode and a second electrode of a battery operably coupledwith the battery charger. The power supply may further be configured toapply an alternating current (AC) energy through the second conductor toat least one of the first electrode and the second electrode of theoperably coupled battery.

Yet another aspect may involve various possible battery designs thatincorporate a patterned layer that affects resonance, and moreparticularly may affect resonance of the anode and the effect of the ACsignal on the anode and the overall effect of suppressing dendritegrowth among other advantages. In one example, a battery may comprise afirst electrode (e.g., an anode) and an ion transport layer including afirst side and a second side, the first side operably coupled with thefirst electrode. The battery may further include a second electrodeoperably coupled with the second side of the ion transport layer, and apatterned layer operably coupled with the first electrode where thepatterned layer is configured to receive an AC energy distinct from acharge or discharge energy.

Additional embodiments and features are set forth in part in thedescription that follows, and in part will become apparent to thoseskilled in the art upon examination of the specification, or may belearned by the practice of the embodiments discussed herein. A furtherunderstanding of certain embodiments may be realized by reference to theremaining portions of the specification and the drawings, which forms apart of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments are illustrated in referenced figures of thedrawings. It is intended that the embodiments and figures disclosed areto be illustrative rather than limiting.

FIG. 1 depicts a cross-section view of the layers of a typical batterycell.

FIG. 2A depicts a cross-section view of the layers of the typicalbattery cell with common problems illustrated for lithium metalbatteries.

FIG. 2B depicts dendrite growth in a battery cell during charging.

FIG. 2C depicts damage to a solid electrolyte interphase layer of abattery during discharge of the battery.

FIGS. 3A-3B depict a first power supply and a second power supply,respectively, for introducing an electrical waveform across a surface ofa first electrode of a battery cell.

FIG. 4 is a flowchart of the methods described.

FIG. 5 depicts a comparison of plating on a copper electrode with andwithout transverse current, showing suppression of dendrite growththrough the application of the method of FIG. 4.

FIG. 6 depicts a comparison of a control sample and an experimentalsample of dendrite growth through the application of the method of FIG.4 on a copper electrode.

FIG. 7 depicts a comparison of dendrite peak height of a control sampleand peak heights of various experimental samples with differentfrequencies of transverse current following the application of themethod of FIG. 4 on a copper electrode.

FIG. 8 depicts a comparison of average height of dendrites on a controlsample and average heights of experimental samples with differentfrequencies of transverse current following the application of themethod of FIG. 4 on an electrode of a battery.

FIG. 9 depicts dead lithium and SEI damage of a battery anode due todendrite growth at the surface of the electrode.

FIGS. 10A-10C depicts common battery cell constructions.

FIG. 11 depicts the propagation of an electro-magnetic (EM) pulse on anelectrode of a coin battery.

FIG. 12 depicts component layers of a modified coin battery cell.

FIG. 13 depicts simulation results applying an electric waveform alongan electrode of a battery.

The present disclosure may be understood by reference to the followingdetailed description, taken with the drawings as described above. It isnoted that, for illustrative clarity, certain elements in variousdrawings may not be drawn to scale, may be represented schematically orconceptually, or otherwise may not correspond exactly to certainphysical configurations of embodiments.

DETAILED DESCRIPTION

Provided herein are methods, devices and compositions whichelectrochemically bond or rearrange metals on surfaces, particularly onan electrode of a battery. Generally, the methods and devices operate bydelivering alternating current (AC) energy at the electrode, such asinducing an AC current across a surface of an electrode of a batterycell, the current being approximately transverse to an electrochemicalcurrent, such as a DC charge current, carried by ions diffusing betweenthe anode and cathode of the battery. Generally, the electrolyte isadjacent to the surface of the electrode, forming anelectrode-electrolyte interface, where metal from the electrolytecontacts the surface of the electrode and passes charge across theinterface to create a current during the electrochemical process. Byinducing an AC current across the surface of the electrode transverse tothe electrochemical current (or otherwise delivering AC energy to theelectrode) electrons at the surface experience a forward compression andrearward expansion of their electric field. This compression andexpansion generates a relativistic charge propagating outward from theelectron's center at the speed of light. The relativistic charge thenbends the field lines of the electrochemical current (e.g., the DCcharge current), directing metal from ions in the electrolyte orpartially adsorbed atoms or particles on the surface to diffuse and formmore uniformly along the electrode surface. More particularly, metalions or surface particles are directed into cracks and crevices, pitsand voids, and high-aspect surface features on the electrode. Asdiscussed in more detail below, this leveling effect on the electrodeduring a charge-discharge cycle of a battery may reduce the growthpotential and/or growth size and/or rate of dendrites along the batteryelectrode and otherwise suppress surface irregularities and roughnessthat otherwise form in conventional battery electrodes, effectivelyprolonging the battery's life, improving the performance, and avoidingexothermic events behind overheating, fires, and explosions.

The methods and devices described herein may operate to induce anelectric potential across the surface of the battery electrode. Theinduced potential bends the field lines proximate the surface so metalfrom the electrolyte follows a path of the bent field lines to depositthe metal onto the surface. In one specific example, the inducedpotential affects the field lines. These bent field lines ultimatelyintersect the surface, including irregularities in the surface, at 90degrees to the portion of the surface being intersected. Viewed anotherway, the bent field lines of the first current alter the trajectory ofthe metal from the electrolyte as it deposits onto and is bonded to thesurface, so the metal has a lower probability of reaching the overallsurface at 90° relative to the electrode's macro-surface on itsapproach, but rather conforms to the surfaces's micro-level contours andirregularities, and exhibits a leveling behavior on the surface. Thus,the metal from the electrolyte may be directed away from dendritegrowths or other irregularities in which dendrite tend to grow. Bydirecting the metal into this “leveling” effect, the electrode of thebattery may resist dendrite growth, thereby preventing damage orinoperability of the battery.

The induced potential of the current, and more generally energy, appliedat or along the surface of the electrode can be controlled by tuning theAC waveform, including its voltage or amperage and frequency. Multiplewaveforms may be combined to tune into different features or substancescomprising the surface of the workpiece. In some instances, the extentof dendrite growth or other electrode surface irregularities can bemonitored in real-time, so the transverse current can be modulated todirect electrochemical processes on the electrode. The process describedherein may improve the formation of the interphase between theelectrolyte and the electrode, referred to herein as the SolidElectrolyte Interphase (SEI), by creating a level or uniform SEI layeralong the surface of the electrode.

FIG. 1. depicts a representative section view of the layers of a typicalbattery, also referred to herein as a battery cell. In general, abattery converts chemical energy to electrical energy. As show in FIG.1, a battery 100 may include a first current collector layer 102(sometimes referred to as a cathode current collector), a cathode layer104, which may be referred to as a cathode alone or in combination withthe adjacent current collector layer, an ion transport medium layer 106,which may be an electrolyte, an anode layer 108, and a second currentcollector 110 (sometimes referred to as a anode current collector)adjacent the anode layer, which may be referred to as an anode alone orin combination with the adjacent current collector layer. Duringoperation, the anode 108 releases ions to the electrolyte 106 that arecollected at the cathode 104. The first current collector 102 and thesecond current collector 110 are typically a conductive metal thatpasses electrical charge to and from the adjacent anode or cathode. Manydifferent types of battery structures exist (including batteries withdifferent electrolyte materials for the anode 108 side of the batteryand the cathode 104 side of the battery), but the general operationdescribed herein applies.

Batteries are often categorized by the materials that makes up the anodeor the ion transport layer 106 of the battery 100. For example, lithiumbatteries have a lithium based anode 108 and ion transport layer 106,such as lithium-metal batteries (Li⁺ containing electrolyte or similarwith a lithium foil anode) and lithium-ion batteries (Li⁺ containingelectrolyte or similar with Li+ containing graphite anode). Other typesof batteries are relevant, including zinc batteries and lead acidbatteries, which are known to those of ordinary skill in the art.Although this discussion exemplifies lithium-ion batteries(lithium-intercalated into graphite), the methods disclosed herein alsoapply to other battery types, including lithium metal, lithium silicon,zinc and lead acid batteries.

When organic electrolyte is used, both types of lithium batteries (amongother battery types including Li-Silicon) form a solid electrolyteinterphase at the interface of the anode 108 and electrolyte 106 as thelithium chemically reacts with the electrolyte. The interphase is alayer comprising the insoluble inorganic and partially soluble organicreaction products which collect at the interface. This layer may bereferred to herein as the SEI layer, discussed above. In general, Liions pass through the interphase or SEI from the anode 108. Because theinterphase generally has a higher impedance, non-uniformity of the solidelectrolyte interphase across the anode 108 can cause uneven currentdistribution across the anode. This unevenness encourages channels toform through the interphase where Li concentration is high. Thesechannels lead to the formation of dendrites. In other instances,irregularities along the surface of the anode 108 may also encouragedendrite growth.

More particularly, dendrites typically grow during charge cycles of abattery as lithium plates/deposits onto the anode surface 108.Electrodeposition proceeds across the interface of two phases via acharge-exchange mechanism between a polarized surface and oppositelycharged ions dissolved or suspended in electrolyte. The mechanism isusually comprised of multiple steps wherein an ion may undergo a partialor full charge exchange, and may diffuse across the surface partiallyadsorbed before settling. Growth mechanisms can be distinguished as 2D(layer by layer type) or 3D (nucleation-coalescence). The prevalence ofeither mechanism depends upon the initial condition of theelectrochemically active surface, the overpotential of the drivingvoltage relative to the thermodynamic energy barriers of each, and theproperties of the electrolyte.

Though no two metals exhibit identical material properties and growthbehavior during electrodeposition, most electrodeposits tend towardrough structure and morphology with increasing thickness. Putting asidethe impact of electrolyte chemistry, low surface energy crystal facestend to grow faster over time. As one crystal face starts to dominate,the grain structure of a deposited layer may change from small andrandomized to columnar in nature. This is true for the deposition ofboth copper and lithium, though the two have significantly differentelastic and reactive properties that impact their relative morphologiesin a battery cell.

FIGS. 2A and 2B illustrate common problems that may occur on a surfaceof an electrode of a battery 200. The battery of FIG. 2A includes thesame layers as the battery described above with relation to FIG. 1, suchas a first current collector layer 102, a cathode layer 104, an iontransport medium layer 106 or electrolyte, an anode layer 108, and asecond current collector 110. The figure also shows a solid electrolyteinterphase 112. As shown in the diagram 200, a dendrite 214 has grownfrom the anode 108 of the battery 200 through multiple charge cycles ofthe battery. FIG. 2B illustrates the problem caused to the effectivenessof the battery 200 from the growth of dendrites 214. In particular,dendrite growth occurs on the anode 108 during charging of the battery.These dendrites begin to block the lithium ions from reaching otherareas on the surface of the electrode, thereby preventing them fromparticipating in the reaction. These ions may also form other dendrites,further increasing the ineffectiveness of the battery. Limiting thegrowth of dendrites on the electrodes of the battery 200 may thusimprove the operation and life of the battery.

Another issue in a battery through a charge cycle is the creation of anirregularity in the SEI 112, causing a weak spot 218 in the SEI layer 12between the electrolyte 106 and the anode layer 108, which issue is alsoillustrated in FIG. 2C. During discharge of the battery, the dendritesthat have formed on the electrode 108 may be partially dissolved backinto the electrolyte layer 106. However, the dendrites do not dissolveuniformly and the connection with the anode base 108 may weaken. Theremains of the partially dissolved lithium may lose electrical contactwith the surface and no longer participate in the reaction. This mayleave a weak, thin area in the SEI layer 112 and/or the anode surface.The SEI 112 be able to immediately reform in the damaged area, causingan irregularity 218 in the surface.

Returning to FIG. 2A, another common problem that arises through acharge-discharge cycle of a battery 200 are non-conductive metaldeposits 216 (sometimes known as dead lithium 216 or other inertcollections of metal) in the electrolyte 106. In some instances, roughfeatures may form along the surface of the electrode 108 that arefragile, such as mossy and fractal lithium. These growths may eventuallybreak from the surface 108 and lose electrical contact. As a result, theenergy potential of this metal mass is no longer available for powerstorage and battery capacity is permanently lost. Each of these issuesmay be addressed through the application of an AC energy signal at oralong the electrode 108.

Conventional techniques to prevent rough deposits have included chemicaladditives, known as brighteners and levelers, which are often used inthe surface finishing industry for electrodeposition and electroplating.Pulse plating and modulated signal techniques offer improvements andcontrol over electrodeposition that are better theoretically predictedand more easily transportable from one metal chemistry to the next.However, the benefit of these approaches to a lithium system, wherereaction rate and diffusion layer thickness are heavily dependent uponan SEI layer, is less clearly defined. For example, a pulse may cause anelectrode to temporarily reverse its polarity (Reverse Pulse Plating) soas to periodically re-dissolve rough edges that may be forming beforethey grow significantly. However, when applied to a battery, the pulsemay disrupt the battery's output power.

These issues may be more prevalent in certain types of batteries than inothers. For example, pure lithium metal batteries have a much higher(˜5-10×) energy capacity compared to lithium ion, but there is littleknown in the art of how to control dendrite growth. The primary obstaclepreventing commercial adoption of lithium metal batteries is theinability to routinely electrodeposit lithium onto the anode withoutdestructive and dangerous dendritic growth, which also leads toelectrolyte consumption, low Coulombic efficiency, and eventual cellfailure. It is especially challenging to identify potential solutionsthat do not compromise the capacity or operating voltage of the battery,and that are applicable over the entire range of form factors nowrequired across industries and products. Currently, these batteriestypically last only through ten charge-discharge cycles. Failure isoften instantaneous and severe when compared to common lithium-ionbatteries.

In addition, as batteries become smaller with increased power capacitythese issues have been amplified and pose significant designconstraints. The lifetime and performance of batteries based uponlithium or any other chemistry may be greatly prolonged by increasingthe smoothness and uniformity of electrode surfaces using the techniquesand apparatus of the present disclosure. This could also allow forincreasing the rate of recharge without compromising the lifetime of thebattery as with conventional batteries.

Described herein are methods and devices for controlling dendrite growthon electrodes and reabsorbing growths into the electrolyte in batteries,improving the performance and life of the battery. In some embodiments,the methods and devices may be operated during DC charging of thebattery to stymie or lessen the formation of dendrites on electrodes ofthe battery. Additionally, the methods may be executed during otheroperational states of the battery to provide additional benefits to thelife and performance of the battery, such as leveling an interphaselayer of the battery or dissolving growths into an electrolyte layer.Controlling or lessening the growth of dendrites in the battery may alsoresult in a relatively more durable battery. In general, through theapplication of an AC signal at or across an electrode of the battery, auniform time-averaged current distribution across the entire surface maybe maintained as compared to conventional techniques without suchalternating energy forms to the electrode (e.g., anode), to more evenlydistribute concentrations of lithium ions or other charge transferspecies throughout the solid electrolyte interphase to maintain ananode/electrolyte interface with uniform electrical behavior.

Method

In view of the preceding introduction, as well as issues and limitationsrelative to conventional processes, provided herein are electrochemicalapparatus and methods for controlling the deposition process on anelectrode of a battery through electrical mitigation or otherelectrokinetic effects of surface features (e.g., dendrites) of theelectrode. FIGS. 3A and 3B illustrate example devices for practicing themethod discussed herein and FIG. 4 illustrates an example methodaccording to the present disclosure. In particular, the method 400 ofFIG. 4 may be executed during a charging cycle of a battery to suppressor reduce dendrite growth on a surface of an electrode of the battery.Referring to FIGS. 3A, 3B and 4, a system 300 may determine when abattery is in a charging operation state (410). When a battery chargeris connected, it may or may not be charging, and depending on state ofcharge or other factors, the level of charging may be more or less. Forexample, during later phases of charging, nearing 100% state of charge,charge current may be reduced. Similarly, current draw from a batterymay be more or less depending on a load on the battery. During a chargecycle of the battery, a current may be induced across the anode (420),which may be an alternating or non-DC current across the surface of theelectrode. During lesser charge levels or lesser discharge levels,relatively greater AC energy may be applied and hence the induced ACenergy may be dependent on charge (or discharge state). As discussedherein, AC energy levels may further be a function of physical andmaterial properties of the particular battery system. If the chargecycle process is incomplete (430), the transverse current along theelectrode may be modulated (440) to adjust the applied AC energy to theanode. So, for example, AC energy application may be adjusted based onstate of charge, temperature, impedance measurements, and other feedbackmechanisms. If the charge cycle process is complete, the processterminates (450). In some instances, AC energy may continue asreabsorption of orphan lithium or other materials may be reabsorbed intothe anode (or cathode) as the case may be.

Referring in more detail to FIGS. 3A and 3B, a battery environment 300is illustrated. In particular, the environment 300 includes a cathode320 electrode, an anode 310 electrode, and an electrolyte 340 adjacentthe cathode and anode. During charging of the battery, ions 324 includedin the electrolyte 340 are collected at the anode 310. Further, throughthe method described, a power supply 360 may be in electricalcommunication 363 to at least a single contact point on the anode 310(FIG. 3A) or more than one point of the electrode FIG. 3B. The powersupply 360 may thus provide an AC energy signal or wave 350 at and/oracross surface 311 of the anode 310 through the contact point or pointson the anode. A single point of contact can create a wave across thesurface, particularly when the current has a path such as being absorbedby the electrolyte. This applied AC energy, which may be an AC current350, is induced across the first electrode 310, which makes ittransverse to a first (charge) current 330 between the cathode andanode. The second current 350 induces a relativistic charge 312 inand/or across a surface 311 of the first electrode 310. In someembodiments, the device includes a power supply 161 in electricalcommunication 161 with the source for a countercharge 120 and inelectrical communication 162, 163 with the first electrode 110. Thepower supply, which may involve more than one device depending on theimplementation, may provide and control the first current 130 and thesecond current 150.

More particularly, the transverse current 350 can be applied at, throughand/or across the surface 311 of the first electrode 310 to affectsurface electrons and induce favorable properties in the deposit withoutaltering the design parameters of the electrolyte 340. In the presenceof the AC energy at the electrode, the electrons at the surface 311experience a forward compression and rearward expansion of theirelectric field. This compression and expansion generates a relativisticcharge 312 propagating outward from the electron's center at the speedof light. The relativistic charge then bends the field lines,conventionally not bent during charge, of the electrical/chemicalreaction, directing metal from the electrolyte to form on the electrodein a controlled fashion with surface roughness suppressed. Viewed inanother way, the induced potential bends the field lines proximate thesurface so metal from the electrolyte follows a path of the bent fieldlines to deposit the metal onto the surface. The bent field linesultimately intersect the surface, including irregularities in thesurface, at 90 degrees within close proximity to the portion of thesurface being intersected. The difference between a point of depositionunder the induced potential and a point of deposition without theinduced potential is a shift of the field lines toward crevices andrough areas of the surface not normally filled. The AC energy to theanode can augment many aspects of the electrodeposition processes thatoccur in a battery during a charge/discharge cycle, including, but notlimited to, two-dimensional growth (smoothness and uniformity); grainproperties, such as crystallinity and morphology; induced nucleation onenergetically difficult surfaces; reduced porosity in the metal;adhesion onto the substrate; and controlled linear crystalline growth.

This change in the electron distribution then alters the behavior ofmetal atoms approaching the surface. Conventionally, the charge densityis greater around irregularities of the workpiece, which then promotelayers of metal to build up the irregularities even more. Instead, inthe disclosed method, atoms are encouraged to follow a path to generatea smooth surface, because areas that would have a large charge densityabsent the transverse current have a lower than typical charge density,and areas with a small charge density absent the transverse current havea greater than typical charge density. The frequency of the transversecurrent's waveform can be swept through several values so irregularitiesof many sizes may be modulated. In one particular embodiment, thefrequency of the transverse current waveform may range from 100 Hz to300 GHz.

Device

The present disclosure also provides a device for performing the methodsdescribed herein. In particular, a device may be utilized for providingan AC signal to an anode of a battery cell. The signal may be appliedthrough a single point of contact with the electrode 310 or through twopoints of contact. The device may include a current generation source,such as power supply 360, to induce a current 350 along the electrodesurface as described in the example methods contained herein. In someembodiments, a main control unit (MCU) 363 may be included to controlthe current source.

The power supply may include the MCU or otherwise be associated with thesame, and the MCU may include a processor or other compute components incommunication with a memory or other tangible storage medium includingsoftware forming executable instructions or control sequences to performvarious methods discussed herein, a computer-controlled power modulator,and auxiliary electronics. In the main control unit, the processor isconfigured to execute the instructions stored on the computer readablemedium. The power modulator and the power supply may be controlled bythe MCU. The MCU may include one or more additional electricalcomponents for providing any signal to the battery electrode. The chargecurrent and AC energy connection point to the electrode may be shared,in some embodiments.

In still other embodiments, the system may utilize an existing chargingcircuit in electrical communication to provide the AC energy signal tothe electrode of the battery. For example, a power supply (chargingsupply) of a personal computing device (such as a cell phone, laptop, orother mobile computing device that may run off battery) may be modifiedto provide the AC energy signal to the anode of a battery included inthe device. In another example, a battery management system (BMS) of avehicle may be modified to transmit currents to the electrodes of abattery or discreet batteries of a larger pack to achieve the methodsdescribed herein. In embodiments discussed herein, conventional chargedevices may be modified with appropriate control schemes to provideconventional DC charge with the addition of an AC signal applied at theanode. For example, in addition to conventional charge electronics,plugs, conductors and the like, a conductor may provide a path betweenthe anode a power supply portion of the charger, and the power supplyconfigured to provide the AC signal to the anode under control of theMCU.

Dendrite Mitigation

The methods described herein control various possible forms of uneven,rough, and/or non-optimal surface effects including dendrite growth anddendrite precursor growth on an electrode or electrodes in many types ofelectrochemical structures such as batteries including, but not limitedto, lithium metal batteries, lithium-ion batteries, lithium silicone,zinc batteries, lead acid batteries, and the like. The method may beexecuted on an electrode of a battery to provide multiple electrodynamiceffects, including suppressing growths of dendrite on the electrode ofthe battery.

The method, in particular embodiments, involves generating tailoredwaveforms and applying those waveforms to the electrode, which may be incombination with a charge current, in order to excite in the surface atfrequencies correlating to specific resonances of the electrode ordesirable patterns of induced current density. Independent of itsapplication environment, a real world conductive surface is prone to aparticular charge distribution based on geometry and intrinsicproperties. Resistive losses attenuate the power across the surface.Current density is larger at curved or sharp points and electric fieldpotential lines ultimately approach the surface orthogonally. For thesereasons, independent of electrolyte, a polarized electrode experiencesan uneven charge distribution absent the techniques set out herein.

During conventional electrodeposition that occurs during charging abattery, for example, electrons are uniformly dispersed tangentially tothe electrode surface due to mutual repulsion of their electric fields.But tangential points may not be parallel and curved features appear toallow electrons to bunch together. Such an area can attract more metalions and evolve dendrites. By using AC energy to shift these chargesfrom a high energy area to an adjacent area for a statisticallysignificant period of time, the native charge distribution of theelectrode can be altered along with the overall deposition pattern.

As the wavelength of the AC (λ_(AC)) decreases in size and approachesthe length-scale of the electrode, or those of a feature on theelectrode, the energy changes from capacitive to inductive in nature.That is, with an electrode length-scale<<λ_(AC), there will be apotential gradient across the surface from one end to another. Themagnitude of that gradient is greatest when each electrode end isspatially matched to the maximum and minimum of the waveform (˜λ_(AC)).When the electrode length-scale>>λ_(AC), many points of maxima andminima will exist leading to a higher occurrence of inductive energy atthe surface. This phenomena may affect adsorption, surface and bulkdiffusion, and nucleation processes even though the frequencies are muchfaster than the characteristic times of those processes.

Contrary to conventional pulse or modulation techniques at lowerfrequencies, high frequency AC is subject to continuous superposition ofincident and reflected energy throughout the system that will interactconstructively or destructively at different points along the surface.For this reason, it is not necessarily the applied transient waveformthat must be considered, but rather the resulting standing wave pattern.Frequencies above ˜200 MHz saturate and exceed relaxation times of mostelectrolytes despite negligible contributions from ions moving withoutan ionic cloud (known as the Wien Effect). Lack of high frequency ionicconductivity through the electrolyte causes the anode and cathode to beconsidered, and potentially modified, independently.

The electrolyte will modify the electrode's native electrical behaviorat the interface in predictable ways. The electrolyte will absorb aportion of the AC energy due to its conductivity, attenuating the signalover distance. This may be overcome by selecting a waveform andfrequency whose incident and reflected energy combine constructivelysome distance from the point of application of the signal on theelectrode. For example, the incident energy may constructively combinewith the reflected energy to provide areas along the surface of theelectrode where a high energy signal is present. Further, thepermittivity of the electrolyte will determine a degree of dielectriccontraction of the waveform.

The amplitude of the waveform presents a possible control parameter ofthe effects of the AC energy on the electrode. For example, control ofAC energy frequency or amplitude may be utilized to tune the AC energywaveform applied to the electrode. A resulting standing wave may be usedto cause a rough area of the electrode to stay below a thermodynamicpotential boundary, or a smooth area to exceed it. Similarly, currentdensity may be focused away from a particularly rough area to preventadditional dendrite growth in that area. Through an analysis of thecondition of the electrode surface, the peaks and troughs of the appliedAC energy wave may be determined to select which portions of theelectrode surface have a higher or lower current density. Underconditions where the frequency and amplitude are great enough, thepotential difference between adjacent areas of the surface of theelectrode may induce localized galvanic reactions, with or without acounter-electrode. The implications of this phenomena for dissolvingdendrites and homogenizing the SEI layer in a lithium based battery isclear.

Low frequency AC power exhibits DC-like behavior relative to theelectrode. As the AC increases in frequency the power focuses closer tothe surface according to the skin effect. In an ideal conductor expectedskin depths are 2 mm at 1 kHz, 2 μm at 1 GHz, and so forth. That is,most of the AC power is focused into a much thinner subsection of thesurface of the anode at higher frequencies. When the interface is morecomplex, such as when the thickness of roughness and the skin depth aresimilar, most of the AC power can then be said to reside at theinterface. Consequently, the efficiency of the AC power is related tothe applied frequency and less power may be necessary at higherfrequencies.

Several experiments were completed utilizing copper electrodeposition asan analogue for lithium metal on an electrode of a battery. The testsdemonstrated initial feasibility to dramatically suppress formation ofdendrites in an aggressive test environment designed to generate mossydendrites. Control tests to generate dendrites were run on copperelectrodes 500 using fully saturated electrolyte solution of cupricsulfate in deionized water. Additives or other methods to reducedendrites or roughness were intentionally excluded. Charge currentdensities for the control were ˜65 mA/cm2. In more detail, FIG. 5illustrates a snapshot of a control sample 500 with greater than 60%surface coverage of mossy dendrites compared to the same test conditionsrun with an AC signal applied across the electrode. As shown, the samplewas run with the noted charge current density and without AC energy (endview of sample 504 and side view of sample 506) and with AC energy (endview 508 and side view 510) with an aggressive electrolyte (low purity,reagent grade, saturated copper sulfate), oxygen containing coppercounter-electrodes, excessive current densities (65 mA/cm{circumflexover ( )}2), unsymmetrical cell (surface area ofcounter-electrodes>working electrode), and long deposition times (8 hrs)(process 502). The approach, as shown in views 508 and 510, eliminatedlarge amounts of the mossy dendrite surface coverage as compared to theapproach without AC energy (views 504 and 506).

In particular, FIGS. 5 and 6 (as well as FIGS. 7 and 8) show resultsfrom the application of an AC signal with a frequency of 75 kHz and apower of 23 dBm to the electrode 500.

To execute the experiments related to FIGS. 5 and 6, a DC power supplyand an AC power generator were employed. The signal from the ACgenerator and the DC negatively polarized power were both connectedindependently to a T-junction. A wire ran from this junction to the testcell. The DC positive polarization is connected directly to the counterelectrodes of the test cell. The AC generator line contained a DC filterinline and upstream of the T to block DC current from flowing into thesignal generator. Similarly, the DC power supply includes an AC filterinline and upstream of the T to block AC energy from flowing into thepower supply and disrupting DC current and voltage measurements. Such aconfiguration may be employed, generally speaking, in a battery charger.The results illustrate dramatic reductions in mossy dendrite surfacecoverage while achieving desired performance on deposited mass relativeto control results. In addition to virtual elimination of mossy dendritesurface area, peak and average surface height in the area of depositionwas reduced by >50% as shown in FIG. 7 and FIG. 8, respectively. InFIGS. 7 and 8, each block (relative to the respective controls)illustrates variability within the respective data set represented by arespective block, with each diagram illustrating respective trends ofdecreasing dendrite height for each data set relative to the respectivecontrol of each Figure.

FIG. 13 depicts simulation results applying an electric waveform alongan electrode of a battery. In particular, the simulation resultssections (a)-(i) of FIG. 13 were generated through a simulation of aconductive electrode in aqueous conditions (p=1.68 E-8 Ωm, σ_(soln)=5S/m, ϵ=80) or Lithium battery/organic electrolyte conditions(ρ_(Li)=9.28 E-8 Ωm, σ_(soln)=1 S/m, ϵ=45) materials. An AC energysignal was applied along the surface of the electrode in a mannersimilar to the methods described herein. A conductive electrode is afoil conductor that is 6 mm wide, 35 μm thick w/w/o 1 mm triangularroughness. A cross-section view of the conductor is illustrated best insection (d) that illustrates the triangular roughness of the surface ofthe foil conductor.

Sections (a)-(c) illustrate various AC energy signals applied to theconductor during simulation. In particular, section (a) illustrates a9.9 GHz AC energy signal, section (b) illustrates a 10 GHz AC energysignal, and (c) illustrates a 100 GHz AC energy signal. Further,electric field (arrows), magnetic field (contour lines), and currentdensity are also illustrated for each signal showing the skin depth (δ)in aqueous conditions.

Section (d) illustrates a current density profile (gray scale) due to aDC signal (approximating the charging current on the electrode) and theroughness of the surface. Thus, section (d) illustrates the case whereno AC signal is applied along the surface of the electrode. Rather, onlythe DC charge current is applied to the electrode. As can be seen, thecurrent density in this case is collected around the points of thetriangular roughness portions of the electrode. It is at this pointsthat dendrite growth is likely to continue. Stated differently, thereare three areas of higher current density at the tips of each triangularroughness, causing more current to flow at those areas, and fastergrowth at those areas as a result.

In contrast, section (e) illustrates a current density profile(grayscale) from the application of an AC signal along the surface of asmooth conductor. As can be seen, the electric field and current densitycan be artificially manipulated by applying an AC energy signal to theelectrode. So, for example, using the system and method discussedherein, the points of high density of a conventional system (e.g, (d))may be distributed away from the peaks reducing or eliminating dendritegrowth. Further manipulation of the parameters of characteristics of theAC signal may tune the current densities as desired. In section (e) (ACpower), there is no triangular roughness (e.g., like in (d) but insteadthe surface is flat. Despite that fact, using AC energy, the system andmethod induce three distinct areas of higher current density indicatedby the U-shaped lines from the flat surface, which lines show themagnetic field behavior. By manipulating frequency and power of the ACenergy, the system can change the spatial location of these lines and ofhigher current density (and faster rate of deposition) across theelectrode.

Sections (f)-(h) illustrate a time-averaged behavior with an applied ACsignal of 100 GHz. High frequency can induce significant transientelectric and magnetic field effects despite being much faster thancharacteristic times of charge transfer and convective processes (˜0.1ms-10 s) (section (f)). High conductivity and permittivity of aqueousconditions (section (g)) add difficulty to uniform current distributionusing a fixed frequency. In (f)-(h), the arrows represent the vector ofthe electric field and the contour lines represent the intensity of themagnetic field, in the presence of the AC signal. More realisticconditions for a Lithium battery (Li metal or Li ion) (h) allow moreuniform energy distribution, and therefore, lower required AC power.These conditions are a promising indicator that, even at high RF, ACenergy should be largely confined to the electrode and electrolyteinterface, imparting a homogenizing effect across the SEI, disruptingdominant ion channels and helping it evolve more rapidly and uniformlyin response to the stresses from expansion or contraction of theinterface. High frequencies that affect capacitive and inductivecoupling of the surface to conductive objects not in direct contact willprovide a means of dissolving and reclaiming dead lithium, regardless ofthe operational state of the battery.

Without AC energy, (f) would look exactly like (d), which shows highercurrent density at the tips of the roughness and electric field arrowsthat primarily point straight down toward the electrode, except nearrough triangles which cause the field lines to bend. In (f), AC energycauses dramatic bending of the electric field arrows, as well asrandomization of the current density in the electrolyte above theroughness. In this case, the roughest areas are no longer growing fasterthan flatter areas of the electrode. In (g) and (h) with AC energy,everything is identical except that in (g) the electrode and electrolytehave the dielectric properties of a water-based chemistry, whereas (h)has the dielectric properties of a lithium ion battery with organicelectrolyte. In (g), the pattern and colorization across the surface ismuch less uniform than in (h), which indicates that the AC energy willbe more uniformly distributed across a lithium battery electrode thanthe water-based copper experiment.

Section (i) illustrates a magnification of a current skin depth, as wellas lateral current distribution at a fixed frequency. Areas of differentgray scale show how current density is spatially distributed as afunction of frequency. As can be seen in the section, current densityalong the surface of the electrode represented by variations in lightand dark gray is altered through the application of the AC energysignal.

Lithium Ion Intercalation

In addition to dendrite control and mitigation, the application of atransverse AC energy/current at the surface of an electrode may providefurther benefits to the operation and maintenance of a battery. Forexample, during charging of a lithium ion battery, lithiumintercalation/diffusion within the graphite is a rate-determining step.Fast charging at the cell's voltage limit leads to potentially excessiveconcentration polarization. Continuous operation under such conditionsmay cause a thickening of the SEI layer leading to increased systemresistance. It may also cause lithium to begin plating onto thegraphite. This rapidly leads to the same problems encountered in lithiummetal batteries, beginning with formation of lithium dendrites.

AC energy and transverse current (applied via transmission orconductively direct to the anode) may be used to excite lithium ions andincrease the rate of intercalation without the need to increase thecell's DC voltage across the electrolyte. The electrical conductivityalong the graphene plane (σ˜2.5E5 S/m) is three orders of magnitudegreater than that between planes. This facilitates the energy topropagate primarily along the plane of Li ion diffusion, between thegraphite edges that serve as entry and exist points for lithium ions. Atslower frequencies (less than about 1000 Hz), the AC energy may augmentthe diffusion of ions directly, while at higher frequencies the ACenergy may serve to further excite intercalating ions over energybarriers of surface diffusion and intercalation with less potentialacross the cell. As during pretreatment steps (discussed later), theapplication of the AC energy to the electrode avoids adverse effects ofconcentration polarization, including thickening of the SEI anddisruption of the cathode. Increasing the intercalation rate can alsoenable the cell to be run more intensively with less risk of initiatinglithium plating.

Electrolyte-Electrode Interface and SEI

The SEI, as explained above, is a layer comprised of byproducts thatform as lithium reacts with components of organic electrolyte. It existsin all Li-ion, Li—Si, and Li-metal batteries except those that useinorganic membranes instead of organic membrane or electrolyte. Thelayer typically has a lower ionic conductivity and higher viscosity thanthe bulk electrolyte and dominates diffusion and charge transferprocesses in the cell as a result. Lower conductivity and often higherpermittivity also allow the AC/RF signal to propagate more uniformlyacross the electrode surface, resulting in less power being used for theAC/RF signal.

Ideally, the SEI is uniform across the entire electrode. As theelectrode surface expands and contracts or develops rough features withbattery cycling, the SEI may not adapt rapidly enough and can becomethinner in some areas than others. This may be problematic in Li—Sibatteries due to the electrode experiencing unusually large distortionbetween charge-discharge cycles. Because the SEI is a resistive barrierfor dissolved Li in the electrolyte migrating to the electrode, more Lican diffuse through thinner areas of the SEI and deposit unevenly.Dominant ion transport channels can also form through the SEI and becomethe basis for dendrites.

One method to combat the thinning of the SEI on an electrode of abattery is to apply AC energy to the electrode. This energy may beapplied during a charge cycle or when the battery is dormant to reviveweakened portions or level the SEI layer. In general, the applied ACenergy is partially absorbed by the SEI as it traverses the electrodesurface. This may induce charge transfer reactions and accelerate theadaptation of the SEI to the changing electrode surface geometry. The ACcan add a degree of mixing to the charge transfer activity that detersthe onset of dominant ion transport channels. It can also increase thelocalized current density and cause deposits to become dense and lessfragile, abating mossy or fractal dendrites which can break from theelectrode surface, losing electrical contact to become “dead lithium.”

Some lithium batteries may forego organic liquid electrolyte in favor ofa conductive glass or polymer ion transport layer (frequently amembrane, but not always). In the absence of any electrolyte to reactwith the lithium, there may be no SEI. Dendrites are less problematic inthis scenario, either because the surface is less susceptible to theirformation or the solid ion transport layer physically blocks theircontinued growth toward the cathode. However, the electrode surface willcontinue to age and degrade. In these instances, the glass or polymerlayer still provides a dielectric medium with low conductivity, and thusstill facilitates the efficient propagation of AC energy for chargeredistribution and the general prevention of surface non-uniformities.

The effect of the applied AC energy may be to thin or to thicken theSEI, depending upon conditions and waveform parameters to address manyirregularities in the SEI layer. Control over one or the other may bemost available when AC energy is applied while the cell is neithercharging nor discharging, but rather in a dormant state.

Pre-Treatment of New Electrodes for Initial SEI Formation

An optimally evolved SEI layer on the anode is often critical to theperformance of a lithium ion battery. Prior to distribution,manufacturers will subject the unpackaged electrode material, and later,the packaged electrodes, to a variety of time and energy-intensivepretreatment steps that usually span several weeks. Pre-treatment stepswill often include cycling and heat and become energy and timeintensive.

In general, the graphite of an electrode is porous and must becompletely wetted by the electrolyte during an initialization phase toaccess the battery's full capacity. In many applications, however, thesurface tension of the electrolyte makes this difficult and slow forsmall scale porosity at 200 nm or less. This porosity accounts for asubstantial portion of the graphite's total surface area. Wetting istypically achieved under vacuum and heat over days to weeks, making itthe slowest part of the pre-treatment process. Yet it is critical tolater formation of an optimal SEI layer.

Later, the packaged electrodes undergo a series of slow charge-dischargecycles under a temperature control program to properly evolve an initialSEI layer that is dense, thin, electrically insulating, and comprised ofnon-reactive, non-soluble inorganic lithium species. This is known asformation cycling. These cycles are completed slowly, usually 1/10th to1/20th the rate of a normal cycle (0.05 to 0.1 C). This contributes to aprocess lasting several weeks and involves significant use of energy.These steps involve both electrodes in a cell and the conditions thatare needed to optimize the SEI at the anode are not ideal for thecathode. Formation cycling depletes the cathode of a portion of itslithium content, shortening the total battery life, before the cellreaches its end application.

The use of AC energy to excite the anode described in the methods above,either by transmissive or conductive application, provides a way ofimproving both electrode wetting and SEI formation steps in the batterymanufacturing process. AC energy, particularly at higher frequencies,has the notable behavior of inducing strong localized electric fieldgradients, as well as much higher localized current densities. This typeof localized energy density can be used to overcome the capillary forcesthat oppose complete electrolyte wetting of the graphite, requiring lessor no time under vacuum and heat as the energy is applied directly tothe graphite. Localized electrical and magnetic energy buildup can alsostimulate charge transfer processes at one electrode only, evolving anoptimal solid-electrolyte interphase at the anode without polarizing,depleting, or otherwise involving the cathode.

Because conductivity of graphite is much greater parallel to thegraphene plane, the energy density at the edges will be relatively highat most frequencies of interest. As it is where most chemical reactionsare occurring, and as the entry and exist point for intercalating Liions, it is along the edges where the quality of the SEI is mostimpactful to the process. It is therefore useful from the standpoint ofenergy efficiency and propagation that the application of AC energy canbe targeted to specific areas to provide the most benefit. Specifically,AC energy may be applied as a single electrode process to quicklydevelop the initial SEI at edges, with less concern for developmentelsewhere.

Enemy Coupling With Dead Lithium

As described above, rough features may form on the electrode surfacethat are more fragile, such as mossy and fractal lithium. They mayeventually break from the surface and lose electrical contact. FIG. 9illustrates such dead lithium in the electrolyte layer 108 of thebattery due to fragile dendrite growth on the anode 108. The storedenergy potential of this lithium mass is no longer available for powerstorage and battery capacity is permanently lost when such masses form.

The method for providing AC energy to the anode 108 may aid indissolving these dead lithium masses back into the electrolyte 106 andrestoring the energy potential of the battery 100. In particular, the ACenergy can non-conductively induce charges into dead lithium thatinitiate dissolution into the electrolyte 106. Capacitive or inductivecoupling can occur close to the surface depending upon frequency.Closest to the surface, electric or magnetic energy will dominate and alarge portion of the energy will be reactive. If dead material isfarther from the surface, the mechanism of energy transfer will bedominated by more coherently radiated energy. These two mechanismsapproximately correspond to the near field and far field regions of aradiating body, respectively. Even in the case of radiated energy, thedead matter will have its own near-surface coupling phenomena thatresults in reactive energy. By inducing current into the dead matter,local current density can be sufficiently increased for charge transferprocesses and dissolution. In a dissolved state, the matter is onceagain accessible for energy storage.

Reabsorption may be monitored in various ways. For example, over variouscharge and discharge cycles, with AC energy applied during charge and/ordistinctly, storage capacity may be monitored each successive cycle. Insome instances, capacity may be compared to a stored capacity value setor measured initially when the battery is put into service, or may becompared to a trend of measurement over time (e.g., decreasing capacityor distinct decreases in capacity over time, as compared to increases incapacity after reabsorption processing). Reabsorption may also bedetermined based on cell resistance with a decrease in resistancerelative to a previously measured value indicating reabsorption of deadmaterial present at the time of the previously measured value.

Single Point of Contact

Batteries traditionally only have one point of electrical contact withan electrode. For example, FIGS. 10A-10C illustrate three common cell orbattery formats and the externally accessible points of electricalcontact. In particular, FIG. 10A illustrates a top view of a pouch cell1002 that includes sheets of electrodes and ion transport layers whichare cut to specific dimensions. The cutout for the electrodes includes atab 1004 that can be accessed for providing electrical contact. In somecases, additional tabs may be added at different points to enablemultiple points of contact, if needed. However, typically there is onlya single point of electrical contact 1004 per electrode. In the exampleillustrated, a first tab 1004(A) is to the counter-electrode, and asecond tab 1004(B) is to working electrode (e.g., anode). AC energy maybe coupled at the tab 1004(b) or a separate tab 1004(C) may provide aconnection point to the working electrode. Alternatively, AC energy maybe applied across or between tabs on the same electrode, such that anAC(+) connection is made at one tab and an AC(−) connection is made atanother tab.

FIG. 10B illustrates a representative section view of a coin or buttonbattery cell 1006 that contains standard layers inside a ‘can.’ The topand bottom of the can are electrically insulated from one another by agasket 1008. A single point of electrical contact 1010 is made bytouching the bottom of the can anywhere within the area. The can is indirect electrical contact with the current collector layers (usuallyaluminum at the cathode and copper at the anode). FIG. 100 illustrates a“jelly roll” battery 1012 that is based upon rolled multilayers mostsimilar to the pouch cell 1002. But the packaging typically restricts toa single point 1014(A) and 1014(B) of electrical contact per electrode,as with the coin cell.

Although batteries provide a single contact point to the anode, the ACenergy discussed herein may still be applied to achieve the performanceresults of the battery. For example, FIG. 11 illustrates a single pointcontact providing AC energy to an anode 1106 of a coin or button batterycell 1008. 3D views showing an EM pulse (1108 and 1110) propagatingacross the anode surface at different times and from different singlecontact points (A—centered 1102, B—offset 1104). In general, when thewavelength>>anode diameter, location of the contact point is lessimportant. When wavelength≤anode diameter, reflections along theboundaries of the electrode will contribute to more complex patterns andstanding waves across the surface. Thus, because batteries are oftenlimited to a single point of contact, consideration is made to theeffect on the standing AC wave created based on the location of thesingle point of contact on the anode.

Transmitted RF Signal

Instead of being conducted via a source in direct electrical contact,AC/RF may be transmitted to the electrode over a distance to inducesimilar benefits as described herein. In this case, the directivity ofthe transmitter and the orientation of the electrode within the radiatedfield are the primary considerations. In some implementations, such aslarge battery packs, anode access may be limited or challenging. In suchcircumstances, strategically placed transmitters may be positionedthroughout the battery pack to radiate AC signals to the electrodes ofthe cells in the battery pack. In some situations, shielding ordirectional antennas may be deployed to shield the cathode or otherwiseonly direct energy to the anode in circumstances where the anode is theonly target.

Anode and Cathode Independent Modulation

In some instances, the AC signal may not necessarily be appliedproportionally or inverse-proportionally at both the anode and cathodeof a battery. Rather, a signal input at the cathode may affect the anodevia conductance, coupling, or transmission (depending on frequency), andvice versa. In such cases, AC energy can be used to cause batteryhealing (homogenization of the electrode/electrolyte interface) whetherthe battery is active or dormant. If the AC signal is sufficient toinduce localized diffusive and charge transfer processes, homogenizationcan occur at an electrode regardless of whether the battery is charging,discharging, or resting.

The frequency and power of the AC energy should be chosen so as toachieve the desired effect (dendrite prevention, SEI thinning orthickening, ion intercalation, etc.) in the most energy efficiencymanner possible. Overall process efficiency is important to batterycharging and in most applications small decreases in efficiency carrysignificant implications for the application. Calculation of overallefficiency requires combining the energy input between both electrodes(DC, standard) with that used for AC energy, as a ratio against thestorage capacity, lifetime (total cycles), or similar metric of thebattery. In one instance, AC may increase ion intercalation, loweringthe galvanic potential required. In another instance, AC energy mayimprove the healing rate of the SEI following structural changes in theelectrode, increasing the battery's lifetime. The benefit of additionalenergy for the AC signal must be weighed against these outcomes case bycase.

Situations involving fast charging, particularly for large systems suchas EV battery packs or stationary applications, may be more tolerant ofadditional energy for the AC input because the energy requirements ofthe DC input are already high (the relative additional burden on thesystem may be low). When charging, the AC input may be targeted to deterdendrite formation and the development of uneven porosity in the SEI(including ion channels), and increase Li diffusion without (or despite)increasing the cell potential. It may also regulate SEI growth andprevent the layer from becoming too thick. As the cell is discharging,stimulating ion diffusion out of the graphite remains valuable.

AC energy applied during discharge or when the cell is dormant may alsoprovide a calmer environment for the SEI to be healed (re-form at areasof electrode deformation, or re-densify after conditions that havecaused the SEI to become porous), and regain uniformity after aggressivecharge cycles or operating conditions. Further, dead lithium andexisting dendrites may be dissolved at any of these stages.

Electrokinetic Flow and Diffusive Effects

Electrodynamic behavior as the AC energy propagates across the electrodecan give rise to electrokinetic effects at the electrodelelectrolyte,electrode|SEI, SEI and SEI|electrolyte interfaces. The nature of theseeffects depend upon the material properties of one layer relative to theother at an interface. For example, high frequencies well outside ofconventional consideration, such as 100 GHz, when applied at anelectrode can alter steady state diffusion patterns in the electrolytenear the surface. The exact pattern is frequency dependent.

As previously discussed, the magnitude of the localized charge density,electron pathways, and the local electric field gradient all depend uponthe frequency and generally increase proportionally. Exceptions mayarise under certain conditions of resonance (energy becomes capacitiveor inductive in nature) or energy absorption by the surroundingenvironment. When the applied frequency is slower than the chargerelaxation time of a layer, conduction mechanisms will dominate thepassing of charge to and from the interface. If conduction dominates inone layer but not the other then the interface will become polarized. Ifthe applied frequency is faster than a layer's charge relaxation timethen interfacial polarization will be proportional to the difference inthe permittivity of the two layers.

The basic behavior of any interface in response to AC energy can beestimated based upon the general guidelines above and the relativeproperties of all layers. This can be the simplest basis for starting todetermine a proper waveform to achieve a particular effect:

-   Electrode (Lithium): High conductivity, Low Permittivity-   SEI: Low conductivity, Medium permittivity-   Organic Electrolyte: Medium conductivity, Medium-High permittivity.    Regardless of which interface is considered, at frequencies    approaching or exceeding resonance across the interface's dimensions    or features, the affects becomes mixed and spatially dependent—i.e.,    localized. The correct frequency and power may induce    dielectrophoretic forces that create patterns of diffusion at or    near the surface. Stated differently, the frequency and power of a    given AC energy application can be based upon the difference in    electric and dielectric properties of the materials inside the    battery.

Engineered Battery Cells

In the cases discussed thus far, the nature of the applied energy andmechanism of its effect on diffusive and charge transfer processes maydepend upon the relationship of the applied wavelength compared to thedimensions of the electrode. Specifically, how resonant is theelectrode, or features on the electrode, at the applied frequency. Thisis the appropriate focus for battery systems whose electrochemicalbehavior should be modified by the process without changes to the cell'sgeometry or design.

In cases where the battery can be re-engineered, a tailored (patterned)resonating layer can be added in close proximity to the electrode toguide or form the energy applied to the surface of the electrode. Forexample, FIG. 12 illustrates component layers for a coin cell batteryformat 1200. In this manufactured cell, the anode 1202 is modified witha dielectric 1204 and a conductive/patterned layer 1206 for electricalcoupling with the primary conductive layer. Examples pattern layers A-C1218-1212 shows various patterned layers that may be included in thecoin cell 1200. As shown, the geometry of the patterned layer 1208matches the primary layer in example A. In example B, the patternedlayer 1210 contains a ring to couple more strongly with magnetic energy.In example C, the patterned layer 1212 contains a complex geometry tocontrol the resonant frequency and induce specific patterns of currentdensity at the primary electrode. In general, the patterned layer 1206may take any shape and size to form or create the AC wave applied to theanode of the cell.

In the case of a modified battery cell, DC energy may be applied to theprimary conductive layer 1202 in contact with electrolyte, while AC isapplied to the patterned layer 1206. The patterned layer 1206 isdesigned with a unique conductive pathway with desired resonant behaviorthat may or may not be similar to the primary conductive layer. A givenbattery layer, and particularly electrode of a battery, will resonatebased on dimensions and material characteristics of the layer. Thepatterned layer can be tailored to resonate, and interact with thetarget battery layer to effect overall resonance in the presence of anAC signal. In one example, computer simulation may be used to develop aspecific pattern for any given application, and tune or otherwise adjustthe pattern for the overall intended impact on dendrite suppression andthe like. AC energy applied to a carefully patterned conductive layercan be made to flow in unique directions that don't necessarily matchthe pattern. If the patterned layer is separate from the electrode by athin dielectric layer, then the electric and magnetic fields that arisefrom the AC energy on the patterned layer will travel through thedielectric layer and impact the electric and magnetic fields on the discelectrode.

In a different case, the primary conductive layer 1202 may be connectedto the patterned conductive layer 1206 via one or more conductivechannels through or around the dielectric layer so that DC and AC can beapplied at a single point and reach both layers. In this case, theresonant behavior of the primary conductive layer 1202 is modified, andpossibly dominated, by coupling with the patterned layer 1206. Thepatterned layer 1206 may also still affect electrochemical processes onthe primary conductive layer 1202 when only the primary conductive layerreceives DC and/or AC conductive input.

The patterned layer may take many forms, as discussed. The resonantbehavior in example A 1208 would be fixed even as the primary layerunderwent changes during operation of the battery. Coupling would occuracross the dielectric layer between the conductive layers. This wouldalso allow the AC signal to propagate more uniformly without attenuationdue to the conductive electrolyte. In another instance, the patternedlayer may be a closed loop that is coupled more strongly with magneticenergy at applied AC frequencies, as would be case with example B 1210.

In another instance, the patterned layer may entail a complex geometrythat shifts the strongest capacitive-inductive transitions (for example,shift resonant points to lower frequencies). The geometry may alsoinduce unique, patterned regions of electromagnetic behavior onto theprimary conductive layer (example C 1212). In one very particular case,the pattern may affect a spoof surface plasmon polariton that inducesdirectional patterns of current displacement. Patterned layer may besubject to no direct conductive input, and instead impact theelectrochemical processes at the primary conductive layer entirelythrough coupling.

Other Battery Types

Zinc batteries have similar or better energy capacity than lithium ion(particularly zinc-air batteries). Zinc and lithium are both negativemetals and when utilized in batteries, they face similar issues withdendrites. A primary difference is that zinc can be used in aqueous(usually alkaline) environments. Dendrites are also a major obstacle inthe ability to cycle Zn electrodes in rechargeable zinc batteries. Theyform readily and can damage or short the anode and cathode. Dendritesuppression may be achieved by the use of organic additives in theelectrolyte, which ultimately become co-deposited into the electrode anddepleted. Small concentrations of various metals or metal oxides mayalso be added to the zinc electrode surface directly to affect thesolubility and mobility of reversible byproducts, maintaining a moreuniform surface during cycling. To prevent the need for these types ofadditives, the processes and methods described herein may be used tosuppress dendrite formation and homogenize the surface of zincelectrodes in rechargeable zinc batteries.

Regarding lead-acid batteries, the methods described herein may bemodified to account for the configuration of the electrochemical celland its electrochemistry. Unlike a lithium-based battery, both the anodeand the cathode plate and corrode during charge and discharge. Existingcells have only two ports, so the transverse current is sent in one portcalculated to reflect off the far wall of the cell and back to the portof entry. The waveform of the transverse current is thus swept throughseveral frequencies to achieve relative balanced time-averaged currentdistribution across the anode and cathode surfaces of the lead acidbattery.

Having described several embodiments, it will be recognized by thoseskilled in the art that various modifications, alternativeconstructions, and equivalents may be used without departing from thespirit of the disclosure. And several well-known processes and elementshave not been described to avoid unnecessarily obscuring the embodimentsdisclosed. So the above description should not be taken as limiting thedocument.

Those skilled in the art will appreciate that the disclosed embodimentsteach for example and not by limitation. Therefore, the matter in theabove description or shown in the drawings should be interpreted asillustrative and not in a limiting sense. These claims should cover allgeneric and specific features described, and all statements of thepresent method and system, which, as a matter of language, might be saidto fall therebetween.

What is claimed is:
 1. A battery comprising: a first electrode; an iontransport layer including a first side and a second side, the first sideoperably coupled with the first electrode; a second electrode operablycoupled with the second side of the ion transport layer; and a patternedlayer operably coupled with the first electrode, the patterned layerconfigured to receive an AC energy distinct from a charge or dischargeenergy.
 2. The battery of claim 2 further comprising: a dielectric layerbetween the first electrode and the patterned layer.
 3. The battery ofclaim 2 wherein the first electrode is an anode.
 4. The battery of claim3 further comprising an interphase layer.
 5. The battery of claim 4wherein the interphase layer is a solid electrolyte interphase (SEI)layer between the anode and the ion transport layer.
 6. The battery ofclaim 1 wherein the patterned layer affects a resonance of the firstelectrode.
 7. The battery of claim 1 wherein the ion transport layercomprises an electrolyte.
 8. The battery of claim 1 wherein the iontransport layer comprises an interphase.
 9. The battery of claim 1wherein the AC energy is an AC current or AC voltage.
 10. A batterycomprising: a first electrode; a patterned layer operably coupled withthe first electrode, the patterned layer to receive an alternatingenergy to affect resonance of the first electrode; and a secondelectrode.
 11. The battery of claim 10 wherein the patterned layer isconfigured to receive the alternating energy distinct from a chargeenergy or a discharge energy.
 12. The battery of claim 11 wherein thefirst electrode is an anode.
 13. The battery of claim 11 wherein thecharge energy is a controlled current or voltage applied to the firstelectrode.
 14. The battery of claim 10 further comprising a dielectriclayer positioned between the first electrode and the patterned layer.15. The battery of claim 10 wherein the patterned layer comprises aring.
 16. The battery of claim 10 further comprising: an ion transportlayer including a first side and a second side, the first side operablycoupled with the first electrode; the second electrode operably coupledwith the second side of the ion transport layer.
 17. The battery ofclaim 16 wherein the ion transport layer comprises an electrolyte. 18.The battery of claim 17 further comprising an interphase layer.
 19. Thebattery of claim 18 wherein the first electrode is an anode and theinterphase layer is a solid electrolyte interphase (SEI) layer betweenthe anode and the electrolyte
 20. The battery of claim 10 wherein thealternating energy is an AC current or AC voltage.